The STROBE Statement (STrengthening the Reporting of OBservational studies in Epidemiology) is the reporting guideline for observational research — cohort, case-control, and cross-sectional studies. It sets out a 22-item checklist of what a published observational study report should contain so readers, peer reviewers, and anyone trying to replicate or synthesize the work can judge how the study was conducted and how much confidence to place in its results.
STROBE was developed by an international collaboration of methodologists, researchers, and journal editors (the STROBE Initiative) and first published in 2007 by von Elm, Altman, Egger, Pocock, Gøtzsche, and Vandenbroucke, on behalf of the STROBE Initiative: “The Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) Statement: Guidelines for Reporting Observational Studies,” PLoS Medicine 4(10): e296 (2007). The same statement was published concurrently in Annals of Internal Medicine and Epidemiology. STROBE is one of the guidelines catalogued by the EQUATOR Network, alongside CONSORT for randomized trials and PRISMA for systematic reviews.
Unlike CONSORT, which was substantially revised as CONSORT 2025, the original 2007 STROBE checklist has not been superseded by a full renumbered revision — the STROBE Initiative has instead published topic-specific extensions (see below) that add items on top of the base 22. As of this page’s last verification date, the 2007 checklist below is still the current base STROBE checklist referenced by strobe-statement.org.
STROBE at a glance
| Question | Answer |
|---|---|
| What it applies to | Observational studies: cohort, case-control, and cross-sectional designs |
| Total items | 22 |
| Items common to all three designs | 18 |
| Items with design-specific wording | 4 (items 6, 12(d), 14(c), and 15) |
| Sections | Title and Abstract, Introduction, Methods, Results, Discussion, Other Information |
| First published | 2007, PLoS Medicine 4(10): e296 (von Elm et al.), concurrently in Annals of Internal Medicine and Epidemiology |
| Maintained by | The STROBE Initiative; catalogued by the EQUATOR Network |
| Companion document | A separate “Explanation and Elaboration” (E&E) article gives methodological rationale and published examples for every item |
The full STROBE checklist (22 items)
The table below reproduces the STROBE checklist exactly as published for reports combining cohort, case-control, and cross-sectional studies. Items marked with an asterisk (*) require information to be given separately for cases and controls in case-control studies, or for exposed and unexposed groups in cohort and cross-sectional studies.
| Section | Item # | Recommendation |
|---|---|---|
| Title and abstract | 1a | Indicate the study’s design with a commonly used term in the title or the abstract |
| 1b | Provide in the abstract an informative and balanced summary of what was done and what was found | |
| Background/rationale (Introduction) | 2 | Explain the scientific background and rationale for the investigation being reported |
| Objectives (Introduction) | 3 | State specific objectives, including any prespecified hypotheses |
| Study design (Methods) | 4 | Present key elements of study design early in the paper |
| Setting (Methods) | 5 | Describe the setting, locations, and relevant dates, including periods of recruitment, exposure, follow-up, and data collection |
| Participants (Methods) | 6a | Cohort — eligibility criteria and sources/methods of participant selection; describe follow-up methods. Case-control — eligibility criteria and sources/methods of case ascertainment and control selection; give the rationale for the choice of cases and controls. Cross-sectional — eligibility criteria and sources/methods of participant selection |
| 6b | Cohort — for matched studies, give matching criteria and numbers of exposed/unexposed. Case-control — for matched studies, give matching criteria and the number of controls per case | |
| Variables (Methods) | 7 | Clearly define all outcomes, exposures, predictors, potential confounders, and effect modifiers; give diagnostic criteria if applicable |
| Data sources/measurement (Methods) | 8* | For each variable of interest, give sources of data and details of methods of assessment (measurement); describe comparability of assessment methods if there is more than one group |
| Bias (Methods) | 9 | Describe any efforts to address potential sources of bias |
| Study size (Methods) | 10 | Explain how the study size was arrived at |
| Quantitative variables (Methods) | 11 | Explain how quantitative variables were handled in the analyses; if applicable, describe which groupings were chosen and why |
| Statistical methods (Methods) | 12a | Describe all statistical methods, including those used to control for confounding |
| 12b | Describe any methods used to examine subgroups and interactions | |
| 12c | Explain how missing data were addressed | |
| 12d | Cohort — if applicable, explain how loss to follow-up was addressed. Case-control — if applicable, explain how matching of cases and controls was addressed. Cross-sectional — if applicable, describe analytical methods taking account of sampling strategy | |
| 12e | Describe any sensitivity analyses | |
| Participants (Results) | 13a* | Report numbers of individuals at each stage of the study — e.g. numbers potentially eligible, examined for eligibility, confirmed eligible, included in the study, completing follow-up, and analysed |
| 13b* | Give reasons for non-participation at each stage | |
| 13c* | Consider use of a flow diagram | |
| Descriptive data (Results) | 14a* | Give characteristics of study participants (e.g. demographic, clinical, social) and information on exposures and potential confounders |
| 14b* | Indicate the number of participants with missing data for each variable of interest | |
| 14c* | Cohort only — summarise follow-up time (e.g. average and total amount) | |
| Outcome data (Results) | 15* | Cohort — report numbers of outcome events or summary measures over time. Case-control — report numbers in each exposure category, or summary measures of exposure. Cross-sectional — report numbers of outcome events or summary measures |
| Main results (Results) | 16a | Give unadjusted estimates and, if applicable, confounder-adjusted estimates and their precision (e.g. 95% confidence interval); make clear which confounders were adjusted for and why they were included |
| 16b | Report category boundaries when continuous variables were categorized | |
| 16c | If relevant, consider translating estimates of relative risk into absolute risk for a meaningful time period | |
| Other analyses (Results) | 17 | Report other analyses done — e.g. analyses of subgroups and interactions, and sensitivity analyses |
| Key results (Discussion) | 18 | Summarise key results with reference to study objectives |
| Limitations (Discussion) | 19 | Discuss limitations of the study, taking into account sources of potential bias or imprecision; discuss both direction and magnitude of any potential bias |
| Interpretation (Discussion) | 20 | Give a cautious overall interpretation of results considering objectives, limitations, multiplicity of analyses, results from similar studies, and other relevant evidence |
| Generalisability (Discussion) | 21 | Discuss the generalisability (external validity) of the study results |
| Funding (Other information) | 22 | Give the source of funding and the role of the funders for the present study and, if applicable, for the original study on which the present article is based |
Source: reproduced from the official STROBE checklist for cohort, case-control, and cross-sectional studies (combined), strobe-statement.org, based on von Elm E, et al., PLoS Medicine 2007;4(10):e296. Verified directly against the primary-source PDF, last verified 2026-08-16.
Which four items differ by study design
18 of the 22 items apply identically no matter which observational design a study used. Four items carry separate, design-specific wording because what counts as an adequate answer genuinely differs by design:
- Item 6 (Participants) — a cohort study describes follow-up methods; a case-control study describes case ascertainment, control selection, and the rationale for that choice; a cross-sectional study describes participant selection alone, with no follow-up to describe.
- Item 12(d) (Statistical methods) — cohort studies explain how loss to follow-up was handled; case-control studies explain how matching was handled statistically; cross-sectional studies explain how the sampling strategy was accounted for analytically.
- Item 14(c) (Descriptive data) — applies to cohort studies only: summarise follow-up time.
- Item 15 (Outcome data) — cohort studies report outcome events over time; case-control studies report exposure by group; cross-sectional studies report outcome events or summary measures at the single time point studied.
These design splits track the same underlying distinctions covered in CASRAI’s case-control vs. cohort study comparison: cohort studies group participants by exposure and follow them forward, case-control studies group participants by outcome and look backward at exposure, and cross-sectional studies measure exposure and outcome at a single point in time.
What the asterisked items mean
Items 8, 13, 14, and 15 carry an asterisk in the official checklist. The asterisk is a single shared footnote, not four separate rules: report that information separately for cases and controls in a case-control study, or separately for exposed and unexposed groups in a cohort or cross-sectional study, rather than pooling the two groups into one set of numbers.
STROBE extensions
Because a base 22-item checklist cannot capture every reporting concern specific to a research area, the STROBE Initiative and affiliated groups have published extensions that add items to the base checklist for particular study types, including STROBE-ME (molecular epidemiology), RECORD (studies using routinely collected health data, such as administrative or electronic health record data), and STROBE-nut (nutritional epidemiology), among others. Authors should check the current extension list at strobe-statement.org for the study type they used — an extension adds to, rather than replaces, the base 22 items above.
How to use the checklist when submitting a manuscript
- Identify which of the three designs — cohort, case-control, or cross-sectional — the study used, since that determines the exact wording of items 6, 12(d), 14(c), and 15.
- Work through all 22 items against the manuscript draft, noting the page or line number where each item is addressed.
- Read the companion “Explanation and Elaboration” article for any item where it’s unclear what level of detail is expected — it gives the methodological rationale and published examples for each item.
- Submit the completed, page-referenced checklist as a supplementary file if the target journal requires or requests one; many epidemiology, general medical, and public health journals do, per their author instructions.
- Treat STROBE as a reporting checklist, not a study-design or statistical-analysis guide — it specifies what to report, not how to design the study or which statistical test to run.
STROBE vs. CONSORT vs. PRISMA: which guideline applies
| Guideline | Applies to | Items |
|---|---|---|
| STROBE | Observational studies — cohort, case-control, cross-sectional | 22 |
| CONSORT | Randomized controlled trials | 30 (CONSORT 2025) |
| PRISMA | Systematic reviews and meta-analyses | 27 (PRISMA 2020) |
If a study randomly assigned an intervention, it needs CONSORT, not STROBE. If it synthesizes results across multiple existing studies rather than reporting new primary data collection, it needs PRISMA. STROBE is specifically for original research where the investigator measured, rather than assigned, exposure. The EQUATOR Network guide on this site is the fuller routing reference for choosing among all EQUATOR-catalogued reporting guidelines, not just these three.
Frequently asked questions
What is the STROBE statement?
The STROBE statement is a 22-item checklist, first published in 2007, that specifies what information a report of an observational study — cohort, case-control, or cross-sectional — should include. It is a reporting guideline: it governs what gets written up, not how the study itself should be designed or analyzed.
How many items are in the STROBE checklist?
22 items across six sections (Title and Abstract, Introduction, Methods, Results, Discussion, and Other Information). 18 items are worded identically for all three observational designs; 4 items (6, 12(d), 14(c), and 15) have separate wording depending on whether the study is a cohort, case-control, or cross-sectional design.
Is the STROBE checklist mandatory for publication?
Requirements vary by journal. Many epidemiology, general medical, and public health journals require or request a completed, page-referenced STROBE checklist as a condition of submission or peer review for observational research; check the specific target journal’s author instructions rather than assuming.
What’s the difference between STROBE and CONSORT?
STROBE covers observational studies, where the investigator measures but does not assign exposure. CONSORT covers randomized controlled trials, where the investigator assigns the intervention. They are companion guidelines maintained by related but distinct initiatives, both catalogued by the EQUATOR Network.
Are there different STROBE checklists for cohort, case-control, and cross-sectional studies?
The STROBE Initiative publishes both a single combined checklist covering all three designs (used on this page) and separate individual checklists for each design, for authors who prefer a version showing only the wording relevant to their study.
Does STROBE apply to studies using routinely collected or electronic health record data?
The base STROBE checklist applies broadly, but studies built on routinely collected health data (registries, administrative claims, electronic health records) should also consult the RECORD extension, which adds items specific to the additional reporting concerns that data source raises.
